The present invention relates to feed systems for television broadcast antennas, and more particularly, for such feed systems when used with helical antennas for producing circular polarization.
Recently, there has been much interest in circular polarization for television broadcasting purposes in order to reduce ghosts in the displayed picture. One kind of antenna for producing circular polarization is shown in U.S. Pat. No. 3,940,772, which uses a plurality of helices wound around a conducting mast. Typically there are four such helices. A coaxial feed transmission line is disposed within the mast, and it must be coupled to the helices to excite them. Typically the coupling means comprises power splitters and transformers to achieve the necessary power division and phasing. Such devices are costly and complex, and further occupy a substantial space which adds to wind loading and icing problems.
It is therefore desirable to have a feed system for a plural coil helix antenna that is less expensive than the prior art, and which provides reduced wind loading and icing problems.